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Carb Question

M

maxtor

Contributing Member
"I want to go buy a Carb rebui

"I want to go buy a Carb rebuild kit and just want to make sure I have the right info. On the carb, one of the screws has a gold plate under it that says:
Mercruiser MCM 120/140
1389-8490

Does this mean it's a Mercruiser Carb or is there some other info somewhere else? It also has:

610366-011
4 7 01 E
on the side of the carb.

I presume all I have to do is give them this info and they will know what I need correct?"
 
"the 1389 number is the part n

"the 1389 number is the part no. for the carb. you haven't given any engine info. if it has two idle adjustment screws, it's a rochester. if one, mercarb. if you are getting the kit from a dealer, give them the serial number from the engine."
 
"Sorry Scott, wasn't sure

"Sorry Scott, wasn't sure how much info was needed. The motor is a 120HP Mercruiser. I believe it only has one idle adjustment screw"
 
"It's a 1985 120 HP Mercru

"It's a 1985 120 HP Mercruiser, Serial number A313692. I just bought the boat last year so I'm not 100% that this is the original carb, but I believe it to be.

Appreciate the help Scott, and the patience
biggrin.gif


You don't need the color of the boat or anything do you?
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"
 
"carb kit= sierra # 18-7097
f

"carb kit= sierra # 18-7097
float= sierra # 18-7202
that's for white, blue, or red boats. green, or purple different."
 
"Thanks for the info. Just a c

"Thanks for the info. Just a curiosity question, where do you find that info out just by knowing the serial number of the motor?"
 
"many places. in this case, ri

"many places. in this case, right on this site. look on the right margin, top catagory.(engine parts) check it out. then order the parts, or at least say thank you to Andrew. good luck with your project. S."
 
"Be careful with the float lev

"Be careful with the float level specs that come with the rebuild kit... I know of at least one case in which they were wrong.
<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_pdf.gif""" align=left alt=""application/pdf"">Mercarb Service Bulletin
[url=""][b]97_08.pdf[/b][/url] (50.4 k)</td></tr></table></center>"
 
"Thanks to both of you Scott a

"Thanks to both of you Scott and Troy. That pdf you gave me Troy was very helpful, and in fact, makes me wonder if a rebuild kit is even needed. Here's what's going on, maybe you would have some suggestions.

Seems to be fine during start up, but once I shut it down, the carb fills with fuel. This seemed to have started after I installed a new Fuel Pump. What would be your recommendations for this?"
 
""once I shut it down, the

""once I shut it down, the carb fills with fuel"

Lee: Are you saying the throat (where the air is sucked in)fills with fuel after it is shut off?"
 
"When you say the float is set

"When you say the float is set too high, what would be the proper procedure for fixing this? I need to bend the float down to shut it off sooner?

I'm looking at the Merc Carb Float Settinds in the PDF that Troy supplied above. I'm guessing that this one would be the one for my carb: (I say that because my carb says MCM 120)

(1) MCM, MIE 5.0L, 5.7L S/N 0L000001 and Above:
Float Level - 11/32 in. (9 mm)
Float Drop - 15/16 in. (24 mm)

What do they mean by "Float Level"? I realize the "Float Drop" means that the Float shouldn't drop any more than 15/16" from Float Level. Correct? Just not sure how to obtain "Float Level". I'm really trying to learn and do all this myself because the Marine place in my area is a scam. They charged me $80 for a stupid little coil."
 
"Found my answer to the above

"Found my answer to the above questions. Really do appreciate everyone's help in here!!!!

Actually, I guess I still need to make sure that the settings for the (1) MCM, MIE 5.0L, 5.7L S/N 0L000001 and Above:
Float Level - 11/32 in. (9 mm)
Float Drop - 15/16 in. (24 mm)

is the one I would use on my carb. "
 
"I think you got it.
The meas

"I think you got it.
The measurement is taken from the gasket sealing surface, with the gasket installed to the toe of the float.
Don't be too surprised if you have to adjust it down from there. At, 3/8" float level, mine actually hit the top of the bowl, before the needle valve shut."
 
"Okay, went to my local Marine

"Okay, went to my local Marine place and bought a Carb rebuild kit and Float. Last time I buy it there I'll tell ya. Almost $90 for the kit and $53 for the float. I never knew a damn float would cost so much. Next time I'll just buy the Sierra kit ahead of time and have it shipped here.

Anyway, gonna rebuild the carb tomorrow and hopefully tomorrow afternoon I can see how it goes!!"
 
You should have walked out on

You should have walked out on the sales clerk and told them you were two bucks short. For another $60 you could have sent it out to Flyingfish Carbs. for a complete remanufacture with the same warranty as Merc. and had it back in a few days.
 
"Question guys. I rebuilt the

"Question guys. I rebuilt the carb and things seem to go pretty good. My question is this:

Just idling in the driveway, with the muffs on, I notice a lot of black stuff floating on the water. I assume this is exhaust but I'm figuring there shouldn't be so much. Does this mean it's running "RICH" or "LEAN"? Also, do I use the adjustments on the choke front, that it shows in the rebuild kit, to correct this?

One more thing, the, I believe it's the "idle adjustment screw" at the base of the carb, the instructions say to turn it all the way in, then back it out 2 turns. However, it seems to idle better if I only back it out about one turn.

I'm getting closer, just need to get this last little bit straightened out.
HUGE thanks for all the help, AND the tube of Preparation H
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"
 
"soot. a little at startup no

"soot. a little at startup no big deal. make sure the choke opens after warm up. you will need to adjust the idle in the water. the two turns is a start point. when you get launched, adjust for best idle. don't worry about it til then. adjustment on flusher will not be right in water."
 
"Good point Scott. Lee: Secur

"Good point Scott. Lee: Secure the boat to the dock fore and aft and put it in forward gear. Now set the idle RPM to specs. and then set the mixture. Recheck the idle RPM and you are set.
All adjustments are made at operating temp. If the stalling still happens, if the accellerator pump lever arm has more than one hole for the pump shaft, change the pump shaft to the hole that provides for the most amount of pump travel to get the most fuel."
 
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